This invention relates to a fluid dispenser, and more particularly to a hot melt adhesive applicator.
Hot melt adhesive applicators including pneumatically actuated needle valves in modular systems for dispensing or discharging small amounts of hot melt adhesive, are well known in the art, as exemplified by the following U.S. Pat. Nos.:
3,094,254 Cullen et al--June 18, 1963 PA1 3,332,580 Spencer et al--July 25, 1967 PA1 3,332,581 Estabrooks--July 25, 1967 PA1 3,348,520 Lockwood--Oct. 24, 1967 PA1 Re. 27,865 Baker et al--Jan. 1, 1974 PA1 3,690,518 Baker et al--Sept. 12, 1972 PA1 3,840,158 Baker et al--Oct. 8, 1974 PA1 4,066,188 Scholl et al--Jan. 3, 1978
The patents to Cullen et al, Estabrooks, and Scholl et al disclose pneumatically actuated needle valves which are mounted in the body structure of the manifold or dispenser head. The disassembly of the elements is quite complex if it is desired to remove, for replacement or repair, the needle valve or the valve actuator.
Although all three of the above Baker patents disclose needle valve cartridges for insertion upon, or into corresponding openings within, a service block or module, nevertheless such cartridges include a body incorporating not only the valve, valve actuator and air chamber, but also a liquid adhesive chamber. Such cartridges contain more elements than necessary for replacement, and further require more seals than necessary to prevent the leakage of air and liquid adhesive.